Aircraft fuel tank inerting system

Abstract

An aircraft fuel tank inerting system may include at least one fuel tank, at least one surge tank, an inert air assembly, at least one fluid valve connected to the at least one fuel tank, the at least one surge tank, and the inert air assembly, and/or an electronic control unit. The electronic control unit may control the at least one fluid valve to provide inert air from the inert air assembly to the at least one fuel tank and/or to the at least one surge tank. The electronic control unit may control the at least one fluid valve to provide inert air from the inert air assembly to the fuel tank during a climb phase of a flight and control the at least one fluid valve to provide inert air from the inert air assembly to the at least one surge tank during a descent phase of the flight.

What is claimed is: 
     
       1. An aircraft fuel tank inerting system, comprising:
 a left wing fuel tank; 
 a right wing fuel tank; 
 a left surge tank; 
 a right surge tank; 
 an inert air assembly; 
 a first fluid valve connected to at least one of the left wing fuel tank and the left surge tank; 
 a second fluid valve connected to at least one of the right wing fuel tank and the right surge tank; and 
 an electronic control unit configured to:
 control a position of the first fluid valve to provide inert air from the inert air assembly to at least one of the left wing fuel tank and the right wing fuel tank; and 
 control a position of the second fluid valve to provide inert air from the inert air assembly to at least one of the left surge tank and the right surge tank, wherein in at least one condition, the position of the second fluid valve is the same as the position of the first fluid valve. 
 
 
     
     
       2. The aircraft fuel tank inerting system of  claim 1 , wherein the electronic control unit is further configured to:
 control the first and second fluid valve to provide the inert air from the inert air assembly to at least one of the left wing fuel tank and the right wing fuel tank during a climb phase of a flight; and 
 control the first and second fluid valve to provide the inert air from the inert air assembly to at least one of the left surge tank and the right surge tank during a descent phase of the flight. 
 
     
     
       3. The aircraft fuel tank inerting system of  claim 2 , wherein the electronic control unit is further configured to control the first and second fluid valve such that, during the descent phase, mixed air is provided from at least one of the left surge tank and the right surge tank to at least one of the left wing fuel tank and the right wing fuel tank, wherein the mixed air includes less than about 20% oxygen. 
     
     
       4. The aircraft fuel tank inerting system of  claim 3 , wherein the electronic control unit is configured to control at least one of the first fluid valve and the second fluid valve such that during the descent phase, mixed air provided from at least one of the left surge tank and the right surge tank to at least one of the left wing fuel tank and the right wing fuel tank includes about 16% or less oxygen. 
     
     
       5. The aircraft fuel tank inerting system of  claim 2 , wherein the electronic control unit is configured to operate at least one of the first fluid valve and the second fluid valve in a closed position during a cruise phase of the flight if at least one of the left wing fuel tank and the right wing fuel tank has achieved an inert margin above a threshold. 
     
     
       6. The aircraft fuel tank inerting system of  claim 1 , wherein the electronic control unit is configured to close at least one of the first fluid valve and the second fluid valve if the electronic control unit determines that an aircraft to which the electronic control unit is connected is on the ground. 
     
     
       7. The aircraft fuel tank inerting system of  claim 1 , wherein the electronic control unit is configured to:
 operate the first fluid valve and/or the second fluid valve in an open position during a climb phase of a flight to provide inert air to the left wing fuel tank or the right wing fuel tank; 
 operate the first fluid valve and/or the second fluid valve in a closed position if the left wing fuel tank or the right wing fuel tank has achieved an inert margin above a threshold; and 
 operate the first fluid valve and/or the second fluid valve in a bypass position during a descent phase of the flight to provide inert air to the left surge tank and/or the right surge tank. 
 
     
     
       8. A method of inerting one or more aircraft fuel tanks, the method comprising:
 operating a first fluid valve and a second fluid valve of an aircraft in an open position during a climb phase of a flight to provide inert air to at least one fuel tank of the aircraft from an inert air assembly of the aircraft; 
 operating the first fluid valve and the second fluid valve in a closed position during a cruise phase of the flight if the at least one fuel tank has achieved an inert margin above a threshold; 
 operating the first fluid valve and the second fluid valve in a bypass position during a descent phase of the flight to provide inert air to at least one surge tank of the aircraft. 
 
     
     
       9. The method of  claim 8 , including:
 mixing inert air from the inert air assembly with ambient air in the at least one surge tank to form mixed air; and 
 providing the mixed air to the fuel tank. 
 
     
     
       10. The method of  claim 8 , including operating the first fluid valve and the second fluid valve in the closed position if the aircraft is on the ground. 
     
     
       11. An aircraft comprising:
 an engine; 
 a left wing and a right wing; 
 a left wing fuel tank in the left wing and a right wing fuel tank in the right wing; 
 a left surge tank in the left wing and a right surge tank in the right wing; 
 an inert air assembly; 
 a first fluid valve connected to the left wing fuel tank, the left surge tank, and the inert air assembly; 
 a second fluid valve connected to the right wing fuel tank, the right surge tank, and the inert air assembly; and 
 an electronic control unit; 
 wherein the electronic control unit is configured to: control the first fluid valve to provide inert air from the inert air assembly to the left wing fuel tank or to the left surge tank, and control the second fluid valve to provide inert air from the inert air assembly to the right wing fuel tank or to the right surge tank, wherein the first fluid valve and the second fluid valve are controlled between a plurality of same positions. 
 
     
     
       12. The aircraft of  claim 11 , wherein the electronic control unit is further configured to:
 control the first fluid valve and the second fluid valve to provide the inert air from the inert air assembly to the left wing fuel tank and/or the right wing fuel tank during a climb phase of a flight; and 
 control the first fluid valve and the second fluid valve to provide the inert air from the inert air assembly to the left surge tank and/or the right surge tank during a descent phase of the flight. 
 
     
     
       13. The aircraft of  claim 12 , wherein the electronic control unit is further configured to control the first fluid valve and the second fluid valve such that during the descent phase, mixed air provided from the left surge tank and/or the right surge tank to the left wing fuel tank and/or the right wing fuel tank includes less than about 20% oxygen. 
     
     
       14. The aircraft of  claim 12 , wherein the electronic control unit is configured to operate the first fluid valve and the second fluid valve in a closed position during a cruise phase of the flight if the left wing fuel tank and/or the right wing fuel tank has achieved an inert margin above a threshold. 
     
     
       15. The aircraft of  claim 11 , wherein the electronic control unit is configured to close the first fluid valve and the second fluid valve if the electronic control unit determines that an aircraft to which the electronic control unit is connected is on the ground. 
     
     
       16. The aircraft of  claim 11 , further comprising a center fuel tank and a third fluid valve, wherein the electronic control unit is configured to control the third fluid valve to provide inert air from the inert air assembly to the center fuel tank. 
     
     
       17. The aircraft of  claim 16 , wherein the electronic control unit is configured to control the third fluid valve to provide the inert air from the inert air assembly to the center fuel tank during a climb phase of a flight and fix alignment. 
     
     
       18. The aircraft of  claim 16 , wherein the electronic control unit is configured to operate the third fluid valve in a closed position during a cruise phase of the flight if the center fuel tank has achieved an inert margin above a threshold. 
     
     
       19. The aircraft of  claim 11 , wherein mixed air is provided from the left surge tank and/or the right surge tank to at least one of the left fuel tank and the right fuel tank.